Toric lens design

ABSTRACT

This invention is related to contact lenses. In particular, the present invention is related to a toric contact lens design with thickness zones in the carrier portion of the lens for increased rotational stability.

This application claims the benefit under 35 USC § 119 (e) of U.S.provisional application No. 60/655,964, filed Feb. 23, 2005,incorporated by reference in its entirety.

This invention is related to contact lenses. In particular, the presentinvention is related to a toric contact lens design with thickness zonesin the carrier portion of the lens for increased rotational stability.

BACKGROUND

Contact lenses are widely used for correcting many different types ofvision deficiencies. These include defects such as near-sightedness andfar-sightedness (myopia and hypermetropia, respectively), astigmatismvision errors, and defects in near range vision usually associated withaging (presbyopia).

Astigmatism is optical power meridian-dependent refractive error in aneye. This is usually due to one or more refractive surfaces, mostcommonly the anterior cornea, having a toroidal shape. It may also bedue to one or more surfaces being transversely displaced or tilted.Astigmatism is usually regular, which means that the principal (maximumand minimum power) meridians are perpendicular to each other. Peoplewith astigmatism have blurred vision at all distances, although this maybe worse at distance or near, depending on the type of astigmatism.These people may complain of sore eyes and headaches associated withdemanding visual tasks. Astigmatism can be corrected with an astigmaticophthalmic lens, which usually has one spherical surface and onetoroidal (cylindrical) surface.

Because toric lenses have a cylindrical surface, orientation of the lensis of particular importance. Hence, most contact lenses have one or moreorientation features that provide a predetermined orientation on theeye. Typical orientation features include two thin zones at the top andbottom of the lens as well as prism ballast.

The present invention seeks to correct the inadequacies of the prior art

SUMMARY OF THE INVENTION

In accomplishing the foregoing, there is provided, in accordance withone aspect of the present invention, a toric contact lens havingmultiple zones in the carrier portion of the lens for increasedrotational stability.

One embodiment of the present invention includes a toric contact lensdesign with a central optical zone, a vertical meridian, a carrierextending from the central optical zone, and a plurality of thicknesszones that are designed to achieve rotational stability. The presentinvention may have one or more transition zones. In one embodiment, atransition zone may be located between the central optical zone 1 andthe carrier. In another embodiment, a transition zone may be locatedbetween the carrier and the lens edge. In a related embodiment, twotransition zones may be present; one located between the central opticalzone 1 and the carrier and another located between the carrier and thelens edge.

In another embodiment, the toric contact lens design includes threethickness zones. In a related embodiment, each thickness zone may havetwo boundaries. In a related embodiment, the second zone is preferablysymmetrical across the vertical meridian on the sides of the lens. Instill another embodiment, the first and third thickness zones may be atthe top and bottom of the lens design. In one embodiment of the presentinvention, the boundary between the first and second zones is about 15degrees from the vertical meridian. In another embodiment, the boundaryis about 25 degrees from the vertical meridian. In still anotherembodiment, the boundary is about 45 degrees from the vertical meridian.

The thickness profiles of the present invention are preferably measuredalong angular meridians. In one embodiment, the thickness profile of thesecond zone increases from its upper boundary to its lower boundary. Ina related embodiment, the slope of the thickness profile of the secondthickness zone may be a linear function, which may be constant or have apositive or negative slope. In another embodiment, the slope of thethickness profile of the second thickness zone may be a step function.In still another embodiment, the slope of the thickness profile of thesecond thickness zones may also gradually increase and subsequentlydecrease from the upper boundary to the lower boundary. At each angularmeridian within the second thickness zone, there is a relativelyconsistent thickness section. The width of the section may be at least30% of the zone width. The thickness profile of the second zone may havea range from the upper boundary to the lower boundary of about 0.065 mmto about 0.45 mm. In a more preferred embodiment, the thickness rangemay be from about 0.140 mm to about 0.340 mm.

The present invention may allow the same carrier to be used fordifferent optical zones on different lenses. The present invention mayalso include lenses having the designs disclosed herein. Such lenses arepreferably soft lenses

These and other aspects of the invention will become apparent from thefollowing description of the preferred embodiments taken in conjunctionwith the following drawings. As would be obvious to one skilled in theart, many variations and modifications of the invention may be effectedwithout departing from the spirit and scope of the novel concepts of thedisclosure.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 schematically shows the components of a basic toric lens design.

FIG. 2 depcits a lens with multiple zones in the carrier according to apreferred embodiment of the invention.

FIG. 3 is a plot showing lens thickness in various zones of a lensaccording to one embodiment of the present invention.

FIG. 4A is a plot that depicts the thickness profile slope in zone 2according to one embodiment of the present invention.

FIG. 4B is a plot that depicts the thickness profile slope in zone 2according to one embodiment of the present invention.

FIG. 4C is a plot that depicts the thickness profile slope in zone 2according to one embodiment of the present invention.

FIG. 5A is a top view of a lens according to one embodiment of thepresent invention sectioned for horizontal slicing.

FIG. 5B is a side view of a lens depcited in FIG. 5A.

FIG. 6 depicts slices of the lens of FIG. 5A

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference now will be made in detail to the embodiments of theinvention. It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the scope or spirit of the invention. Forinstance, features illustrated or described as part of one embodiment,can be used on another embodiment to yield a still further embodiment.Thus, it is intended that the present invention cover such modificationsand variations as come within the scope of the appended claims and theirequivalents. Other objects, features and aspects of the presentinvention are disclosed in or are obvious from the following detaileddescription. It is to be understood by one of ordinary skill in the artthat the present discussion is a description of exemplary embodimentsonly, and is not intended as limiting the broader aspects of the presentinvention.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Generally, the nomenclatureused herein and the manufacturing procedures are well known and commonlyemployed in the art. Conventional methods are used for these procedures,such as those provided in the art and various general references. Wherea term is provided in the singular, the inventors also contemplate theplural of that term.

In one embodiment, the present invention provides a toric contact lensdesign. The toric contact lens of the present invention has a concaveback surface (posterior surface) and a convex front surface (anteriorsurface). The front surface preferably consists of a center opticalzone, a transition zone, and a peripheral carrier. In a preferredembodiment, a rotational stability feature is included in the peripheralcarrier. The peripheral carrier is preferably divided into multiplestability or thickness zones.

In an alternative embodiment, the toric and/or aberration correction inthe central optical zone may be on the posterior surface. In stillanother embodiment, the optics in the central optical zone may be splitbetween the anterior and posterior surfaces of the lens. For example thetoric optics may be located in the anterior surface whereas, forexample, progressive optics (for presbyopia) may be located on theposterior surface.

FIG. 1 schematically shows a typical toric contact lens according to apreferred embodiment of the invention. The toric contact lens 100 mayhave a diameter about 14.5 mm. The toric contact lens 100 preferably hasa concave (or posterior) surface 110 and an opposite convex (oranterior) surface 120, and a central axis passing through the apex ofthe convex (anterior) surface.

The convex surface 120 comprises a central optical zone 122, which iscircular in shape and is substantially concentric with a central axis,and a non-optical peripheral zone or carrier 128.

The central optical zone 122 is a toroidal surface and has a diameter ofabout 8 mm. The toroidal surface is formed by defining a curve in theY-Z plane, wherein the Z-axis coincides with or is parallel to thecentral axis of the lens, and then rotating this curve around an axisparallel to the Y-axis from a distance r the value of which is selectedto impart a desired cylindrical optical power to the contact lens forcorrecting astigmatism errors of an eye.

FIG. 2 depicts the zones used in the present invention to providestability on the front surface of a lens. The carrier 10 may be dividedinto three zones (1,2, and 3). Additionally, this same configuration maybe considered to have 4 zones as zone 2 may be considered as two zones,as the entire area shown in FIG. 2 is not continuous. In a preferredembodiment, zone 1 is preferably located towards the top of the lens andhas the minimum thickness found in carrier 230. Zone 1 is preferablysymmetrical about the vertical meridian. Zone 2 is located beneath zone1 on opposite sides (left and right sides) of the optical zone 1 ndextends between zone 1 and zone 3. Zone 2 is preferably a prism zonewith greater thickness and borders 250 and 260. The thickness of zone 2preferably increases along the angular meridians, reaching a zonemaximum towards the bottom border 260. The right and left sections ofzone 2 are preferably mirrored along the vertical meridian.

Zone 3 is preferably a weight balance zone that has a larger mass thanzone 1. The thickness profile of zone 3 along the vertical axis ispreferably similar to conventional prism ballast toric lenses. In someembodiments the thickness profile may be thinner than conventional prismballast toric lenses.

The central portion of the lens, or optical zone 200 is created usingordinary methods known in the art. In one embodiment, there is atransition zone 210 between the optical zone and the carrier. In arelated embodiment, the may be a second transitional zone near the lensedge 220. In another embodiment, the lens is designed such that atransition zone is not present. Additionally, a transition zone may notbe present at or near lens edge 220 but rather, carrier portion 230 ofthe lens may extend to the edge of the lens.

The present invention defines thickness along slices called meridians.Many inventions, such as those disclosed in U.S. Pat. No. 6,467,903 usemeridians that are horizontal slices to define thickness. In the contextof the present invention, thickness is preferably defined along radialor angular meridians that radiate from the central zone.

Referring back to FIG. 2, zones 1, 2, & 3 may be defined by radialboundaries. For example, the boundary line between zones 1 & 2 may belocated about 15 degrees from the vertical meridian as measured from thetop of the lens. In another embodiment, the boundary line between zones1 & 2 may be about 45 degrees from the vertical meridian. In oneembodiment, the boundary line between zones 2 & 3 may be approximately30 degrees from the vertical meridian as measured from the bottom of thelens. In still another embodiment of the present invention, the boundaryline between zones 2 and 3 is about 60 degrees as measured from thebottom of the lens.

In still another embodiment, the zones may be defined by angles. In thisembodiment, if the vertical meridian is used as a reference, with 12o'clock defined as o degrees, the right side of zone 2, as shown in FIG.2, can be defined between about 15 degrees (upper boundary) and about150 degrees (lower boundary). In a preferred embodiment, the right sideof zone 2 can be defined between about 45 degrees (upper boundary andabout 120 degrees (lower boundary). The lens thickness is preferablygreatest near or at the borders between zones 2 and 3 as shown in thegraphs depicted in FIG. 3. In one embodiment, the thickness range ofzones 2 may be from about 0.065 mm to about 0.45 mm. In a preferredembodiment, the thickness range may be from about 0.140 mm to about0.340 mm.

FIG. 3 depicts the thickness profile within zone 2 of the carrier. Thehorizontal axis represents the radial distance from the junction of thetransition zone and the carrier 230 to the lens edge 220. In thisembodiment, the maximum thickness was located at the border E and theminimum thickness was at the border 250. At each angular meridian, thereis a relatively consistent thickness section, i.e., the thicknesschanges less than or equal to about 10% of the maximum thickness. Thewidth of the section may be at least 30% of the carrier zone width andpreferred 50% of the carrier zone width. The thickness of zone 2 ispreferably used to stabilize the lens.

FIG. 4 represents plots of thickness profile slope in zone 2 for variousembodiments of the present invention. For example, in an embodimentdepicted by FIG. 4A, the slope of the thickness profile may remainconstant. In an embodiment depicted by FIG. 4B, the slope of thethickness profile may be similar to a step-type function. In anembodiment depicted by FIG. 4C, the slope may increase and decrease,reaching a maximum between boundaries 250 and 260.

FIG. 5 maps angular slices taken from a lens produced from oneembodiment of the design of the present invention in various views. FIG.5B represents a section of the lens taken at the vertical meridian.Notably, the lens has a prism-type ballast that is similar to aconventional prism ballast toric lens. In the embodiment depicted inFIG. 5B, the maximum thickness may be approximately 0.321 mm. In oneembodiment the thickness may reach a maximum along boundary 260

FIG. 6 shows individual slices taken from the lens shown in FIG. 5A. Thethickness is preferably greatest in zones 2&3. The sections in FIG. 6are radial sections to better reflect the preference that the lens bethickest along the border between zones 2&3. Although FIGS. 5 and 6contain dimensions, these dimensions are exemplary only and are notmeant to be limiting.

The changes in thickness that create rotational stability may form ageometric thickness pattern that is annular in shape. This ringpreferably has an open end towards the top of a lens, where thethickness is preferably minimal. In this embodiment, the annulargeometry begins along the boundary between zones 1 and 2 and continuesdown through zone 3. The ring preferably has a width of relativelyconsistent thickness, i.e., the thickness changes less than or equal toabout 10% of the maximum thickness at the angular meridian. The annularwidth region is preferably about 1.5 mm wide in zones 2&3 along angularmeridians.

Another parameter that may be used to define the boundaries of theannular region is the percentage of a zone occupied by the annularregion. In a preferred embodiment, the width of annular region mayoccupy at least 30 percent of zone 2. Unless stated otherwise thethickness is measured normal from the posterior surface to the anteriorsurface. Additionally, all distances are measured along the curvedsurface rather than planar projections of the lens.

The present design may be used for various powers. In some embodiments,the thickness profiles of the carrier zones are consistent irrespectiveof the power used. In other words, the same carrier may be used althoughthe optical zone differs. Additionally, the first derivative ispreferably continuous on the entire front surface, thus eliminatingjunctions between zones and areas. This feature may provide greatercomfort to the user.

Any known, suitable optical computer aided design (CAD) system may beused to design an optical model lens, including the carrier zones.Exemplary optical computer aided design systems includes, but are notlimited to Advanced System Analysis program (ASAP) from Breault ResearchOrganization and ZEMAX (Focus Software, Inc.). Preferably, the opticaldesign will be performed using Advanced System Analysis program (ASAP)from Breault Research Organization with input from ZEMAX (FocusSoftware, Inc.).

After completing a desired design, a toric contact lens can be producedin a computer-controlled manufacturing system. The lens design can beconverted into a data file containing control signals that isinterpretably by a computer-controlled manufacturing device. Acomputer-controlled manufacturing device is a device that can becontrolled by a computer system and that is capable of producingdirectly an ophthalmic lens or an optical tool for producing anophthalmic lens. Any known, suitable computer controllable manufacturingdevice can be used in the invention. Preferably, a computer controllablemanufacturing device is a numerically controlled lathe, preferably atwo-axis lathe with a 45° piezo cutter or a lathe apparatus disclosed byDurazo and Morgan in U.S. Pat. No. 6,122,999, herein incorporated byreference in its entirety, more preferably a numerically controlledlathe from Precitech, Inc., for example, such as Optoformultra-precision lathes (models 30, 40, 50 and 80) having Variformpiezo-ceramic fast tool servo attachment.

Toric contact lenses of the invention may be produced by any convenientmeans, for example, such as lathing and molding. Preferably, toriccontact lenses are molded from contact lens molds including moldingsurfaces that replicate the contact lens surfaces when a lens is cast inthe molds. For example, an optical cutting tool with a numericallycontrolled lathe may be used to form metallic optical tools. The toolsare then used to make convex and concave surface molds that are thenused, in conjunction with each other, to form the lens of the inventionusing a suitable liquid lens-forming material placed between the moldsfollowed by compression and curing of the lens-forming material.

Toric contact lenses of the invention can be either hard or soft lenses.Soft toric contact lenses of the invention are preferably made from asoft contact lens material, such as a silicon hydro-gel or HEMA. It willbe understood that any lens described above comprising any soft contactlens material would fall within the scope of the invention.

The invention has been described in detail, with particular reference tocertain preferred embodiments, in order to enable the reader to practicethe invention without undue experimentation. A person having ordinaryskill in the art will readily recognize that many of the previouscomponents, compositions, and/or parameters may be varied or modified toa reasonable extent without departing from the scope and spirit of theinvention. Furthermore, titles, headings, example materials or the likeare provided to enhance the reader's comprehension of this document, andshould not be read as limiting the scope of the present invention.Accordingly, the invention is defined by the following claims, andreasonable extensions and equivalents thereof.

1. A toric contact lens design comprising a central optical zone, a vertical meridian, a transition zone surrounding said central optical zone, a carrier extending from said transition zone outward and a plurality of thickness zones in said carrier, wherein the thickness zones are designed to achieve rotational stability.
 2. The design of claim 1, wherein each thickness zone has two boundaries.
 3. The design of claim 1, wherein the thickness profile is measured along angular meridians.
 4. The design of claim 3, wherein said plurality of thickness zones further comprises three thickness zones.
 5. The design of claim 4, wherein the second said three thickness zones is symetrical across the vertical meridian on the sides of said lens design.
 6. The design of claim 5, wherein the first and third of said three thickness zones are at the top and the bottom of said lens design.
 7. The design of claim 4, wherein the boundary between the first zone and second zone is about 15 degrees from the vertical meridian.
 8. The design of claim 4, wherein the boundary between the first and second zone is about 25 degrees from the vertical meridian.
 9. The design of claim 4, wherein the boundary between the first and second zone is about 45 degrees from the vertical meridian.
 10. The design of claim 4, wherein the boundary between the third zone and second zone is about 30 degrees from the vertical meridian.
 11. The design of claim 4, wherein the boundary between the third and second zone is about 60 degrees from the vertical meridian.
 12. The design of claim 4, wherein the thickness profile of the second zone increases from its upper boundary to its lower boundary.
 13. The design of claim 5, wherein the slope of the thickness profile of the second zone is a linear function.
 14. The design of claim 5, wherein the slope of the thickness profile of the second zone is a step function.
 15. The design of claim 5, wherein the slope of the thickness profile of the second zone gradually increases and subsequently decreases from the upper boundary to the lower boundary.
 16. The design of claim 5, wherein said there is a relatively consistent thickness section at each angular meridian.
 17. The design of claim 5, wherein width of a relatively consistent thickness is at least 30% of the zone width.
 18. The design of claim 5, wherein a thickness change is equal or less than 10% of the maximum thickness at the meridian.
 19. The design of claim 5, wherein a thickness range from the upper boundary to the lower boundary of the second zone is about 0.065 mm to about 0.45 mm.
 20. The design of claim 5, wherein a thickness range from the upper boundary to the lower boundary of the second zone is about 0.140 mm to about 0.340 mm.
 21. The design of claim 1, wherein the same carrier may be used for different optical zones on different lenses.
 22. The lens created by claim
 1. 23. The lens of claim 22, wherein said lens is a soft lens.
 24. The design of claim 1, further comprising a second transition zone at the edge of the lens.
 25. The design of claim 5, wherin said design provides an annular region.
 26. A toric contact lens design comprising a central optical zone, a carrier extending from said central optical zone outward and a plurality of thickness zones in said carrier, wherein the thickness zones are designed to achieve rotiational stability.
 27. The design of claim 26, wherein each thickness zone has two boundaries.
 28. The design of claim 26, wherein the thickness profile is measured along angular meridians.
 29. The design of claim 26, wherein said plurality of thickness zones is three thickness zones,
 30. The design of claim 29, wherein the second of said three thickness zones is symetrical across the vertical meridian on the sides of said lens design.
 31. The design of claim 29, wherein the first and third of said three thickness zones are at the top and the bottom of said lens design.
 32. The design of claim 29, wherein the boundary between the first zone and second zone is about 15 degrees from the vertical meridian.
 33. The design of claim 29, wherein the boundary between the first and second zone is about 25 degrees from the vertical meridian.
 34. The design of claim 29, wherein the boundary between the first and second zone is about 45 degrees from the vertical meridian.
 35. The design of claim 29, wherein the thickness profile of the second zone increases from its upper boundary to its lower boundary.
 36. The design of claim 29, wherein the slope of the thickness profile of the second zone is constant.
 37. The design of claim 29, wherein the slope of the thickness profile of the second zone is a step function.
 38. The design of claim 29, wherein the slope of the thickness profile of the second zone gradually increases and subsequently decreases from the upper boundary to the lower boundary
 39. The design of claim 29, wherein a thickness range from the upper boundary to the lower boundary of the second section is about 0.065 mm to about 0.45 mm.
 40. The design of claim 29, wherein a thickness range from the upper boundary to the lower boundary of the second section is about 0.140 mm to about 0.340 mm.
 41. The design of claim 26, wherein the same carrier may be used for different optical zones on different lenses.
 42. The lens created by claim
 26. 43. The lens of claim 42, wherein said lens is a soft lens.
 44. The design of claim 26, further comprising a transition zone at the edge of the lens. 